Wiring genius: 48v power + data CAN bus

[TruckElectric]

Yes there's pictures of what I described in their patent docs.

Is there a link to the patent docs?

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[JBee]

I think it's a little more than increasing the bus speeds to 1Gb. CAN communications are limited to 500kbps and CAN-FD is limited to (up to) 5Mbps. Moving to 1Gbps ethernet is also implying a redesign of the vehicle network architecture, that I don't think has really been broached yet. As stated before, and restated here for emphasis, current automotive networks consist of a primary Gateway device, which is connected to a few segregated CAN networks. You might have low speed CAN bus for infotainment/comfort systems, one CAN-FD for ADAS (advanced driver assistance system), another CAN-FD for BCM (body control modules), yet another bus for Powertrain modules, etc. Each of these buses are connected to multiple ECUs and can communicate to other CAN busses via the gateway module. However, the ECUs on a bus aren’t based on the physical location in the vehicle; it’s based on it's function and who else it needs to communicate with.

In the example graphic shown above, the PSCM (power steering control module) is positioned near the driver and is connected to the Chassis CAN, but communicates with the Parking Aid ECU, which could be located in the rear bumper. The wiring harnesses for these CAN buses physically connect the ECUs together, then all run to the Gateway, so physically, you have multiple bundles of wires running all over the car for each bus, to connect physically remote ECUs.

Besides speeding up communications of the bus, so you don't need to segregate the various ECUs onto their own buses to prevent collision and throughput issues, I think what Tesla is implementing here is the Zonal Architecture, where one Computer Control Module (CCM) is connected via gigabit ethernet to zonal switches distributed around the vehicle. Those switches are then wired locally to the ECMs close to it, dividing the vehicle into zones (hence the term Zonal).

Note that this graphic states 2025+, so when people state that Tesla is 5 years ahead of other OEMs, this is why. OEMS are just starting to talk about zonal architecture implementation, but you won't hear that name. You'll hear Software Defined Vehicles closely tied to subscription based features.

By clustering the ECU powers in the CCM (I've personally seen inklings of this in Ford and GM), all other features (steering, powered seats, speakers, abs, etc) are reduced to smart actuators, which no longer process their own features, but receive everything from the CCM. OEMS love this because it pulls all the Intellectual property into their in-house CCM unit, and makes OTA updates easier since they don't have to push to each individual ECU scattered across their vehicle networks. As you've heard, it gets rid of tons of wires and copper, and makes it easier to implement subscription based services, because it's no longer about writing config settings CAN on the ECU that controls seat heating, it's just setting a config on the CCM that they have direct control and communication over.

This is of particular interest to me because I'm in a steering software engineer. I work on projects that combine various code features for steering into one package that we write to our PSCM ECU's that go on steering racks we manufacture. I think within 5 years, my job will be very different. There won't be a PSCM ECU communicating out on the CAN bus. Our steering smart actuator will just receive messages from our zonal controller that comes from the CCM and all those steering features won't have to be integrated into our software binary. My company is starting to use Software as a Service buzzwords because that's what we'll be doing; selling our software steering component features to OEMS so they can integrate it into their CCM software.

So TLDR: When you hear Subscription based services in cars, this is part in parcel of a shift to zonal architecture. I'm not positive this is what's going on in the Cybertruck, but combined with statements like "wiring harness reduction" and "gigabit ethernet" I can't see them half-assing the implementation into something other than Zonal architecture.

Your post is spot on target.

The cabling architecture and data rate is the primary cause for removing most of the cable bundles in the vehicle.

The 48V just removes more mass, of the cables that are then left over.

And increases powerline capacity, which is necessary to drive all the nodes.

The EM Monroe interview also makes this clear. EM also admits there that this isn't revolutionary, just that auto makers haven't caught up yet.

 

[JBee]

Is there a link to the patent docs?

I never found a free copy of the whole document from memory just screenshots:

There is another one, that is similar, but I haven't read:

https://patentimages.storage.googleapis.com/7f/ea/45/f221d47693fe6e/US20190217794A1.pdf

There's more discussion from a while back with a bit of a summary here if that helps:

https://www.cybertruckownersclub.co...ck-to-use-48v-instead-of-12v.1639/post-173674

 

[CyberGus]

There are reasons to stick with UTP versus fibre. For instance, the expensive fibre transceivers get hot AF, consuming excess power, with a high failure rate.

 

[SlightlySinged]

There are reasons to stick with UTP versus fibre. For instance, the expensive fibre transceivers get hot AF, consuming excess power, with a high failure rate.

Really only matters when you are looking at transceivers that are in the 40, 100+Gb range. 1Gb, less so. 1Gb transceivers are cheap as hell now too. I do wonder if the fiber itself is more susceptible to shock and vibration loads over time.

 

[Crissa]

Crissa, do you have any of your switches wired like this:?: Router->Switch->Switch->Device (where both switches could have one or more end devices connected.) The daisy chain aspect is that the second switch is not connected directly to the router.

I'm just trying to visualize your wiring better. My mesh WiFi system was a little pricey and I'm wondering it I could have done it with a few more E-net cables and cheap switches.

Well, yeah. I need to replace them with smart switches that report back to the router, but right now the bedroom switch is off the media cabinet switch which is off the router.

Mesh is newer, so it's more expensive, but not because it takes more hardware. It takes fewer wires, fewer chips technically, just not practically.

But I have a little cabin that has conduits and crawlspaces to every corner so I can wire it. I like tech.

My outdoor security camera system use POE. It even powers the small LED lights on the cameras that come on when it senses motion.

Technically, to sense motion, they have an IR beam or photocell or CCD or... well, there's about a dozen ways of doing it, but all involve something being powered about the level of an LED.

-Crissa

 

[FutureBoy]

So, rap music might cause my steering to malfunction in the daisy chain and the suspension might cause my cybertruck to bounce off the road. haha

Good thing I don't listen to that kind of music!

Are you saying that sappy love songs might make my CT curl up in a ball and cry? Or perhaps try to spoon my on the next camping trip?

 

[FutureBoy]

device=peripheral... That's a daisy chain.

Anyone know the history of why the daisy got involved in the chain gang? Daisies themselves evoke a star configuration in my mind...

 

[FutureBoy]

Can I get a reference for how this works?

Probably the best doc would be this:

I'd love to see that thing.

SIDE NOTE:
Anyone know what the subtitle says? I'm very curious now. I mean, it has the word BOOBS. Probably in reference to the people not the body parts or the calculator gag.

 

[wtibbit]

Anyone know the history of why the daisy got involved in the chain gang? Daisies themselves evoke a star configuration in my mind...

I don't have the total, pornographic history, but I did find this NSW image.... Send the kids out of the room NOW!!! (scroll down.....)

 

[FutureBoy]

I don't have the total, pornographic history, but I did find this NSW image.... Send the kids out of the room NOW!!! (scroll down.....)

Ironically laid out in a token ring.

 

[Klyde]

does anyone or anywhere have access to a copy of the 48V doc being sent to major car builders? Would love to dive into the details.

 

[TruckElectric]

@13:25 Sandy mentions "communication over power" guessing he is referring to PoE and Pete Bannon says "no" they use 2 more conductors then explains they have gigabit ethernet, bi-directional for redundancy.

@19:30 Pete Bannon explains the ethernet comms.....says it "looks like a token ring network" then David Lau explains it's a TDMA(Time Division Multiple Access) network.

@39:15 Sandy and Pete look at the 48V "left controller" Pete points out an ethernet loop connection says it's standard twisted-pair shielded cable.

Also when Ganesh Venkataramanan left Pete Bannon took over the Dojo supercomputer project.

 

[Rutrow]

@13:25 Sandy mentions "communication over power" guessing he is referring to PoE and Pete Bannon says "no" they use 2 more conductors then explains they have gigabit ethernet, bi-directional for redundancy.

@19:30 Pete Bannon explains the ethernet comms.....says it "looks like a token ring network" then David Lau explains it's a TDMA(Time Division Multiple Access) network.

@39:15 Sandy and Pete look at the 48V "left controller" Pete points out an ethernet loop connection says it's standard twisted-pair shielded cable.

Also when Ganesh Venkataramanan left Pete Bannon took over the Dojo supercomputer project.

Yeah, they said the POE was too noisy. said they could do it, but it would be too much trouble, so they separated signal from power.

 

[flowerlandfilms]

Maybe they're using Token-Ring networking ?‍

Maybe they are using Tolkien-Ring networking ?‍

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